diff --git a/poky/scripts/lib/wic/filemap.py b/poky/scripts/lib/wic/filemap.py
index 4d9da28..85b39d5 100644
--- a/poky/scripts/lib/wic/filemap.py
+++ b/poky/scripts/lib/wic/filemap.py
@@ -46,6 +46,13 @@
             bsize = stat.st_blksize
         else:
             raise IOError("Unable to determine block size")
+
+    # The logic in this script only supports a maximum of a 4KB
+    # block size
+    max_block_size = 4 * 1024
+    if bsize > max_block_size:
+        bsize = max_block_size
+
     return bsize
 
 class ErrorNotSupp(Exception):